The irrational fear of clowns. Commonly used to get attention or to come off as quirky.
Mike: Hey bro, you wanna go to the carnival later?
Joey: OH NOES! THERE MIGHT BE CLOWNS THERE! I'M SCARED OF CLOWNS!!!! (derpy derp)
Mike: (rolls eyes) Wow, Joey, I can't believe how incredibly quirky you are...